Integrated circuits can include temperature sensors for a variety of purposes including detecting excessive heating in order to shut down circuitry to prevent heat-related damage. For example, circuitry can be damaged by high temperatures, such as heat produced through power dissipation. In such circuits, it may be desirable to produce a signal when a circuit temperature exceeds a safe temperature limit to shut down the circuitry or to alter circuit operation to prevent damage from over-heating or thermal runaway.
Integrated circuits can measure temperature based on a voltage differential between diode-connected transistors, which produce temperature dependent voltages. To convert the voltage differential to a digital scale, some circuits attempt to digitize a ratio of the voltage differential and a temperature independent voltage. However, process variation may produce component mismatches, unintended offsets, and non-idealities (such as different emitter resistances across transistors), which may require trimming and calibration operations to produce the intended linearity across temperatures for a given amount of accuracy/resolution.